Diamond Window Research Articles

Diamond Window into the Lower Mantle

Tiny inclusions in diamonds reveal subduction of oceanic crust to depths of at least 700 km.

New photoacoustic cell design for studying aqueous solutions and gels

A new photoacoustic (PA) cell design, which is particularly suitable for investigations of liquids, gels, and outgassing samples is presented. The setup is based on a PA cell of only 78.5 mm(3) volume, which is sealed on the sample side with either a 163 μm thick chemical vapor deposition diamond window or a 3.91 μm thin diamond membrane. This design offers great advantages compared to traditionally used open-ended PA cells especially when investigating volatile compounds. The new PA cell design is particularly interesting in the studies of biological samples characterized by a high water content. The performance was demonstrated with mid-infrared PA measurements of glucose in aqueous solutions using a tunable quantum-cascade laser as a light source. A detection limit of 100 mg/dl (SNR = 3) has been achieved. Furthermore, the spectral changes of glucose dissolved in water caused by mutorotation have been monitored time-resolved.

Progress on Gyrotrons for ITER and Future Thermonuclear Fusion Reactors

The prototype of the Japan 170-GHz ITER gyrotron holds the energy world record of 2.88 GJ (0.8 MW, 3600 s and 1 MW, 800 s) and the efficiency record of 57%, whereas the Russian 170-GHz ITER prototype tube achieved 0.8 MW with a pulse duration of 800 s at 55% efficiency and 1 MW at 280 s and 53%. The record parameters of the European megawatt-class 140-GHz gyrotron for the stellarator Wendelstein W7-X are as follows: 0.92-MW output power at 1800-s pulse duration, nearly 45% efficiency, and 97.5% Gaussian mode purity. These gyrotrons employ a cylindrical cavity, a quasi-optical output coupler, a synthetic diamond window, and a single-stage depressed collector (SDC) for energy recovery. In order to reduce the costs of the ITER 24-MW 170-GHz ECH&CD system, 2-MW millimeter-wave power per gyrotron tube is desirable. Cylindrical gyrotron cavities are not suitable for the 2-MW power regime because of high ohmic wall losses and mode competition problems. However, in coaxial cavities, the existence of the longitudinally corrugated inner conductor reduces the problem of mode competition, thus allowing one to use even higher order modes with lower ohmic attenuation than in cylindrical cavities. Synthetic diamond windows with a transmission capability of 2-MW CW are feasible. A 2-MW CW 170-GHz coaxial-cavity gyrotron for ECH&CD in ITER is under development in cooperation with European research institutions (EGYC, collaboration among the CRPP, Switzerland, the KIT, Germany, the HELLAS, Greece, the CNR, Italy, and the ENEA, Italy). At the Karlsruhe Institute of Technology (KIT), the short-pulse (1-ms) preprototype tube delivered 2.2 MW at 30% efficiency (without SDC) with 96% Gaussian output mode purity. Design studies for a 4-MW 170-GHz coaxial-cavity gyrotron with two synthetic diamond output windows and two 2-MW millimeter-wave output beams for future fusion reactors are currently being performed at KIT. The availability of sources with fast frequency tunability would permit the use of simple fixed nonsteerable mirror antennas for local current drive experiments and plasma stabilization. IAP Nizhny Novgorod develops in collaboration with IPP Garching and KIT an industrial multifrequency 1-MW gyrotron with approximately 50% efficiency (SDC). A four-frequency tube (105, 117, 127, and 140 GHz) delivered 0.8 MW at 105 GHz and 0.95 MW at 140 GHz in 10-s pulses. After the installation of a broadband diamond window, this gyrotron will be operated also at the two intermediate frequencies.

ECRH for JET: A feasibility study

For JET to fulfil its mission in preparing ITER operation, the installation of an electron cyclotron resonance heating system on JET would be desirable. The study described in this paper has investigated the feasibility of installing such a system on JET. The principal goals of such a system are: current drive over a range of radii for NTM stabilization, sawtooth control and current profile tailoring and central electron heating to equilibrate electron and ion temperatures in high performance discharges. The study concluded that a 12 gyrotron, 10 MW, system at the ITER frequency (170 GHz) adapted for fields of 2.7–3.3 T would be appropriate for the operation planned in JET. An antenna allowing toroidal and poloidal steering over a wide range is being designed, using the ITER upper launcher steering mechanism. The use of ITER diamond windows and transmission line technology is suggested while power supply solutions partially reusing existing JET power supplies are proposed. Detailed planning shows that such a system can be operational in about 5 years from the time that the decision to proceed is taken. The cost and required manpower associated with implementing such a system on JET has also been estimated.

Mid-IR, Far-IR, Raman micro-spectroscopy, and FESEM–EDX study of IDP L2021C5: Clues to its origin

Interplanetary Dust Particles (IDPs) are potentially of cometary origin. They may therefore provide important clues to a better understanding of the early Solar System physical and chemical conditions. A chondritic porous aggregate IDP (named L2021C5) was analyzed using mid to far FTIR (2–60 μm) micro-spectroscopy, Raman micro-spectroscopy, field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) analyses. The IDP was pressed between diamond windows to increase the quality of the spectral data by overcoming the diffraction limitation and minimizing light scattering effects from particles of a global size similar to the wavelength of the observation. This combination of techniques has enabled a mineralogical, organic and compositional description of the compressed particle. The IR spectra show that in L2021C5 amorphous silicates are more abundant than crystalline ones, and that the crystalline component is richer in olivine than in pyroxene. The composition and distribution of these inorganic components match very well the small silicate grains emission observed for comet Hale-Bopp from ISO-SWS spectra. Raman spectroscopy has allowed the detection of carbonaceous structures displaying different degrees of order, covering almost the whole range observed so far for IDPs. The combination of the three analytical techniques indicates that L2021C5 is a low-Ca, chondritic porous aggregate that experienced only mild flash heating on atmospheric entry, as indicated by the disordered carbon properties, the Fe/S atomic ratio of sulfides, the absence of Na depletion, and the small depletion of S. Based on a plausible cometary origin and on the estimated low entry velocity, we suggest that this IDP came from the Zodiacal cloud that is dominated by dust from Jupiter-Family comets.

FT-IR spectra of NaCl–H2O in the region from near to beyond the critical state

Water and NaCl–H2O solutions and their molecular spectra at high temperatures and pressures were observed and examined using a new design of hydrothermal diamond anvil cell (HDAC) connected to both a light and an infrared microscope. We have modified the diamond window of the HDAC to have a wide angle to allow the infrared beam to pass the window. Fourier-transform infrared (FT-IR) spectra of NaCl–H2O–D2O were examined at high temperatures and pressures up to 850 °C and 3 GPa. The effect of increasing temperature on water spectra differed from that of increasing pressure. The O–H stretching frequency of water molecules increases with increasing temperature (from 20 to 600 °C), and also with increasing salinity of the solution.

Development in Russia of Megawatt Power Gyrotrons for Fusion

Tests of the Russian ITER gyrotrons were continued after debugging of the test facility at Kurchatov Institute including the evacuated transmission line and power supplies capable to provide gyrotron CW operation. A new ITER gyrotron (V-10) with upgraded body insulation, liquid cooling system for the DC-break ceramic and improved design of the relief window has been manufactured and is currently under test. A maximal total efficiency near 55% at 1 MW power level was attained. The maximal pulse duration of 1000 s at 0.8 MW power was limited at that time by the test stand. At 1 MW power level the gyrotron V-10 up to now reached a pulse duration of 570 s. An advanced short-pulse (100 ms) gyrotron model operating in the TE28.12 mode demonstrated a very robust operation at relatively high electron energies (up to 100 keV) necessary to achieve 1.5-2 MW output power. Three double frequency gyrotrons have been delivered to ASDEX Upgrade. The development of a multi-frequency gyrotron with a broadband or tuneable synthetic diamond window is in progress.

Nuclear-Safety-Related and Shielding Analyses of the ITER Quasi-Optical ECH Launcher

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Nuclear-safety-related and shielding analyses were performed for the quasi-optical design of the electron-cyclotron-heating launcher installed in the ITER upper port. The critical nuclear responses, affecting the nuclear safety and technical performance of the launcher and nearby components, were calculated using the MCNP5 3-D radiation transport code. The computer-aided design (CAD) interface program McCad was applied for the conversion of the CAD model into MCNP geometry description. The radiation effects of the launcher's halved internal shield were estimated on the chemical-vapor-deposit diamond windows, vacuum vessel, and toroidal field coils. It was revealed that the nuclear-safety requirements were satisfied. </para>

In situ Raman and X‐ray spectroscopies to monitor microbial activities under high hydrostatic pressure

Until recently, monitoring of cells and cellular activities at high hydrostatic pressure (HHP) was mainly limited to ex situ observations. Samples were analyzed prior to and following the depressurization step to evaluate the effect of the pressure treatment. Such ex situ measurements have several drawbacks: (i) it does not allow for kinetic measurements and (ii) the depressurization step often leads to artifactual measurements. Here, we describe recent advances in diamond anvil cell (DAC) technology to adapt it to the monitoring of microbial processes in situ. The modified DAC is asymmetrical, with a single anvil and a diamond window to improve imaging quality and signal collection. Using this novel DAC combined to Raman and X-ray spectroscopy, we monitored the metabolism of glucose by baker's yeast and the reduction of selenite by Agrobacterium tumefaciens in situ under HHP. In situ spectroscopy is also a promising tool to study piezophilic microorganisms.

Romantic Prose Fiction by Gerald Gillespie , Manfred Engel , Bernard Dieterle (review)

320 Reviews The letters tellthestory of howRuskin gradually madeovertherunning, management , and evenownership of Brantwood toJoannaand herhusband Arthur Severn. 'Letters from Ruskin toJoanhaveonlypreviously beenpublished as excerpts and are not generally availableforresearch'(p. 4). The editorsof theLibraryEditionof Ruskin's works included onlya handful of theseletters, and theyfailedto keepthe idiolect, perhaps outofconcern for Ruskin's reputation. Thisreviewer, likeDickinson, finds theletters endearing rather thanembarrassing. Forinstance, Ruskin writes that he'wants hisdimatotakecareofhismoney for him' (p.215).He asks Joannato'please[. . .] beginkeeping mypockywocky money fornext year'(p.217).In Letter 210hesigns off: 'Me's oospoo oldDonie- ' (p.223).In Letter 206heshows hispoeticside: Ohdima,ifI only could build 00a palace with diamond windows andgolden doors, andput on a story [sic] every birth day, asthe shells dointhe sea,andfill itwith music like the seashells. and have my dimatosing tomeupatthe top. (p.218) Ruskin asks Joanna:'fot soodvehavedonetounderstand eachovyifvee'dnevy learnt babytawk?' (p.214). With its'Idiolectical Glossary' anda Chronology, this volume ofletters maybe seen tocontribute towhatone maycallRuskin's 'autobiography', including comments on painting, onfigures, someofthem public ones,andontheevents ofhisownlife. Rachel Dickinson has therefore performed an unusual,useful, and interesting service. The letters shedlighton Ruskin's ownpersonality and psychology, and on howhe saw himself. He insisted that noneofhisletters toJoannabe destroyed, which suggests that he mayhaveconsidered themtobe a partof his'autobiography', tocomplement or supplement whatDickinson describes as the'crafted andcensored' Praeterita. King'sCollege London WilliamGoldman Romantic Prose Fiction. EditedbyGerald Gillespie,ManfredEngel, and Bernard Dieterle. A Comparative History of Literatures in EuropeanLanguages,23. Amsterdam andPhiladelphia: Benjamins. 2007.xxi+ 733pp.€198.00; US$297.00. isbn:978-90-272-3456-8. Collections ofessays dealing with European Romantic culture facesomething ofa challenge :thetopicisdifficult tomap,thedatesoftheso-called 'period'aredisputed and inconstant flux, andthe'movement' continually crosses linguistic, generic, anddisciplinary borders. Asa result, suchvolumes canfallintooneoftwotraps: either they seek toencompass broader trends andendup lacking inclosetextual readings, orthey are sosharply focused that they maybe oflimited appealtomoregeneral readers. Atover 700pages,this volume ofthirty-six essays, together with an Introduction andConclusion ,is morethancomprehensive and makesa goodattempt at circumventing such pitfalls. The fact that thecollection belongs toanintegrated sub-series - theothers are dedicated toRomantic irony, drama, poetry, andnon-fictional prose- helpstoensure that nosingle volume takes ontoomuch. The collection openswith lengthy editorial deliberations, which track thegenesis of theprojectthatgave riseto thevolumeand also,moreusefully, offer conceptual YES, 40.1 & 2, 2010 321 reflections on thesub-series, theposition of thevolumewithin it,and therationale behindthebook'sinternal organization. The essaysare dividedintothreesections, dealing with Romantic prosethemes, thebroadnotion ofparadigms (including representative texts, issues ofgenre, andnarrative technique), andthelaternineteenthand twentieth-century reception of Romantic proseanditsinfluence on laterthought and writing. Throughout thesesections thediscussions traverse the Romanticproseof Germany, France, andEngland, although they alsochart thelegacy left bythis writing inScandinavia, Spain,LatinAmerica, andJapan.Similarly diverse isthetreatment of other mediaanddiscourses, or, more precisely, their intersection with thegenres, themes, andtechniques ofprose, suchas MihálySzegedy-Maszák's study ofrepresentations of the'sister arts'ofmusic andpainting inRomantic prose.Setagainst this richbackdrop are theessaysone might expect, although theyremainessential: thereare thematic contributions, suchas Gerhart Hoffmeister's analysis of howinternational Romantic prosetreats explicitly (Victor Hugo)andimplicitly (Goethe) theprogression andfailure of theFrench Revolution; and MonikaSchmitz-Emans's discussion of theirrational realms of madnessand dream,whichshowshowRomantic prosedealingwithsuch issues laidthefoundations ofkeyaspects of modern thought andwriting, suchas the rejection of'anysuperior levelofreasoning from which onecoulddistinguish between truth andlies'(p.165). Therearegeneric studies, suchasManfred Engel'sremarkably clearandlinear study ofthelabyrinthine genre oftheBildungsroman, andalsolessobvious discussions, suchas GeraldGillespie's treatment ofthecrime novel:whilecrime inliterature was'nothing new',Romantic proseinSpain,England, andelsewhere becametheforum for'a new genre inwhich crime fighters andcrime solvers werecentral' (p.345).Thevolume's third section is particularly illuminating, as shownbyElaineMartin's study of cinematic makesand re-makes of Romantic literary works, and Takayuki Yokota-Murakami's discussion of thecomplex reception and influence of EuropeanRomantic writing in Japan,characterized bybothenthusiasm andrejection, as thatnation openeditself to Western culture inthecourseofthenineteenth century. Sucha wideandinternational focus tiesinwiththeeditors' aims.AstheConclusion states, thevolume doesnotseek toimply that readings ofRomanticism as expressions ofnational experience arewholly irrelevant orevenspurious; rather, itsintention isto'explore strands ofliterary experiencethat often werecommon ona larger regional scale'(p.700). The texts arelucid, readable, andcontain valuablecontributions that simultaneously offer anoverview oftheir material, drawtogether important threads ofscholarship, and re-frame discussions infresh contexts. SabineRossbach, forexample, offers a fascinating sweepof the notionof 'mirroring' in English,GermanRomanticand postRomantic proseembracing E. T. A. Hoffman, Coleridge, and Poe: whilst...

Mantle transect of the Karelian Craton from margin to core based on P-T data from garnet and clinopyroxene xenocrysts in kimberlites

Peridotitic garnet and clinopyroxene xenocrysts from the 1.2 Ga Lentiira–Kuhmo and the 760 Ma Kuusamo kimberlite fields, emplaced within the Central Karelian Craton, have been studied using major and trace element geochemistry to obtain information on the stratigraphy, compositional variability, and evolutionary history of the underlying lithospheric mantle. An earlier study on the 600 Ma Kaavi–Kuopio kimberlite field showed that near the SW margin of the craton the 230-km-thick subcontinental lithospheric mantle (SCLM) exhibits a well-developed 3-layer structure indicative of episodic construction. New Ni in garnet thermometry on samples farther into the craton, from Kuhmo, Lentiira, and southern and northern Kuusamo, gives temperature ranges of 800–1400, 700–1450, 700–1450 and 600–1300 °C, respectively, and when extrapolated to the geotherm determined for the Kaavi-Kuopio area, indicates sampling intervals of c. 100–240, 80–250, 80–250 and 65–210 km, respectively. The results demonstrate that the SCLM of the Karelian Craton reaches its greatest thickness in the Lentiira-Kuhmo and southern Kuusamo area and thins towards the North and South. The mantle stratigraphy of the craton core, compared to the craton edge, shows less compositional variation, with only two distinguishable horizons corresponding generally to the two deepest layers at Kaavi-Kuopio. Additionally, based on the Mg# of pyropes, the level of depletion of peridotites comprising the mantle lithosphere in the central craton is significantly higher than at the craton edge represented by Kaavi-Kuopio. Coupled with the rarity of mantle-derived chrome diopside, the implication is that this portion of the mantle either underwent high levels of partial melting to produce very refractory residua or experienced less melt-modification than average SCLM subsequent to formation. The craton core provides a wide diamond window up to 110 km thick compared to c. 40 km at the craton edge.

Demountable Liquid/Flow Cell for in vivo Infrared Microspectroscopy of Biological Specimens

We have developed a liquid/flow cell/chamber allowing infrared measurements of living biological specimens with high spatial resolution under a controlled aqueous environment. This flow chamber features sub-micrometer thick diamond windows exhibiting low spherical and chromatic aberrations. Diamond has excellent transmission properties and minimal dispersion over the entire mid-infrared and visible spectral ranges. In contrast to current commercially available infrared liquid chambers, the flow chamber has a slim profile, which accommodates high resolution/magnification microscope objectives with small working distances, down to 0.6 mm above the chamber and 6 mm below the flow chamber. We have coupled a pump to the flow chamber to provide medium exchange. As an example, we present microspectroscopic infrared maps and spectra of the freshwater green alga Micrasterias sp. in the new flow chamber and compare them to maps obtained with a conventional liquid chamber. Pulse-amplitude-modulated fluorescence measurements on Micrasterias sp. cells inside the new flow chamber have been evaluated to demonstrate the viability of the algal cells.

Progress of high power 170 GHz gyrotron in JAEA

Recent progress on the high power gyrotron development in JAEA is presented. The gyrotron is featured to have a triode-type magnetron injection gun, a cylindrical resonator working at 170 GHz with TE31,8 mode, a water-cooled diamond window and a depressed collector. After the demonstration of the ITER basic performance, the gyrotron has been operated for 3 years, and recorded ∼200 GJ of total output energy. Next, a gyrotron which oscillates in higher order resonator mode, TE31,12, is designed and fabricated to study the long pulse oscillation at greater than 1 MW. In parallel, feasibility studies of a CW-power modulation for neoclassical tearing mode stabilization, a dual frequency gyrotron and a rapid frequency control are carried out. It is shown that these gyrotrons will be available with current technology.

Distribution of kimberlite and aillikite in the Diamond Province of southern West Greenland: A regional perspective based on groundmass mineral chemistry and bulk compositions

A regional study of dike and sill occurrences of kimberlitic rocks in terms of xenolith and megacryst assemblages from the diamond province in southern West Greenland demonstrates very systematic variation in the composition of melts across the margin of the Archaean core of the North Atlantic craton. Melt derived from the diamond window in the lithospheric mantle below the Archean core in Greenland is kimberlitic. Toward the Palaeoproterozoic Nagssugtoqidian orogen melts (also derived from the diamond window) gradually change to ultramafic lamprophyre compositions evolving toward an end-member akin to the aillikites of the penecontemporaneous Torngat region in Canada. The identification of the types of melts is based on the groundmass paragenesis including the presence or absence of clinopyroxene and chromite, and the compositions of groundmass ilmenite, spinel, and phlogopite. The systematic regional variation is also shown, although somewhat blurred, by the bulk rock major and trace element compositions. The change in melt composition is not a reflection of change in depth of initial melting, but relates to the composition of the deep SCLM. Kimberlite melts in the Archaean craton are suggested to be reaction products between a carbonate-rich astenospheric melt and an orthopyroxene-bearing and phlogopite-poor depleted SCLM, whereas the aillikite type melts across the craton margin are the products of reaction between a similar carbonate-rich asthenospheric melts and a subducted SCLM that had previously been subjected to metasomatism and veining.

A Design to Study Flow Induced Crystallization in a Multipass Rheometer

Abstract The design and performance of a flow geometry for the multipass rheometer (MPR) is described, creating an experimental setup to study in-situ and ex-situ structure and morphology development with a proper control over the processing conditions and shear history. The slit used is equipped with diamond windows, to combine flow with different experimental techniques, such as optical microscopy (OM), birefringence and X-ray scattering. In this paper we present preliminary results, obtained on isotactic polypropylene, that demonstrate the possibilities of this device for more extended future research. The focus is on the in-situ birefringence measurements of crystallization and the relation with the final morphology.

Ultrabroadband terahertz source and beamline based on coherent transition radiation

Coherent transition radiation (CTR) in the THz regime is an important diagnostic tool for analyzing the temporal structure of the ultrashort electron bunches needed in ultraviolet and x-ray free-electron lasers. It is also a powerful source of such radiation, covering an exceptionally broad frequency range from about 200 GHz to 100 THz. At the soft x-ray free-electron laser FLASH we have installed a beam transport channel for transition radiation (TR) with the intention to guide a large fraction of the radiation to a laboratory outside the accelerator tunnel. The radiation is produced on a screen inside the ultrahigh vacuum beam pipe of the linac, coupled out through a diamond window and transported to the laboratory through an evacuated tube equipped with five focusing and four plane mirrors. The design of the beamline has been based on a thorough analysis of the generation of TR on metallic screens of limited size. The optical propagation of the radiation has been computed taking into account the effects of near-field (Fresnel) diffraction. The theoretical description of the TR source is presented in the first part of the paper, while the design principles and the technical layout of the beamline are described in the second part. First experimental results demonstrate that the CTR beamline covers the specified frequency range and preserves the narrow time structure of CTR pulses emitted by short electron bunches.

Mantle xenocrysts from the Arkhangelskaya kimberlite (Lomonosov mine, NW Russia): Constraints on the composition and thermal state of the diamondiferous lithospheric mantle

The Arkhangelskaya kimberlite pipe belongs to the Zolotitsa kimberlite field in the Arkhangelsk region, NW Russia. It is the first pipe of the Lomonosov diamond mine to be put into production, with 2 million tons of ore already extracted. In this study major and trace element compositions of garnet, clinopyroxene (Cpx), Mg-ilmenite and chromite xenocrysts from the Arkhangelskaya pipe have been used to infer information about the compositional variability of the mantle underlying the Zolotitsa field. Single-grain thermobarometry of peridotitic Cpx xenocrysts yields a cool cratonic geotherm that follows a ca. 36 mW/m 2 conductive model. Equilibration temperatures of garnet and chromite grains based on Ni- and Zn-thermometry, respectively, indicate a sampling interval of ca. 70–230 km of the lithospheric mantle when projected onto the Cpx-derived geotherm. The major element chemistry of Mg-ilmenite xenocrysts suggests that almost optimal redox conditions for diamond preservation prevailed in the mantle during the time of emplacement of the host kimberlite magmas. Garnet major and trace element compositions combined with the Cpx-geotherm indicate that the peridotitic diamond window extends from 130 to 210 km under Zolotitsa and that the deeper parts of the lithosphere have been affected by metasomatic events. Arkhangelskaya seems to have sampled the bulk of its diamonds from the deepest portion of the diamond stability field, between 190 and 210 km. In comparison, the neighbouring Lomonosova and Pionerskaya pipes are known to have collected their diamonds from 130–160 km. The comparable grade of the three pipes suggests that diamondiferous material is generously distributed within the diamond stability field. The remarkable difference evidenced by garnet composition and thermobarometry between Arkhangelskaya and the two other Zolotitsa pipes probably derives from differences in rheology and eruption rates of the rising kimberlite magmas.

Low-Frequency Heme, Iron-Ligand, and Ligand Modes of Imidazole and Imidazolate Complexes of Iron Protoporphyrin and Microperoxidase in Aqueous Solution. An Analysis by Far-Infrared Difference Spectroscopy

FTIR difference spectroscopy, notably in the far-IR domain, is appealing for the analysis of hemoproteins, since it permits us to directly probe the properties of the heme and its ligands but also those of aminoacids remote from the heme. We recently set a thin path-length electrochemical cell with diamond windows allowing the far-IR analysis of proteins in aqueous solutions using FTIR difference spectroscopy (Berthomieu, C,; Marboutin, L.; Dupeyrat, F.; Bouyer, P. Biopolymers 2006 82, 363-367). In this study, we used this cell to identify redox-sensitive low-frequency IR modes of imidazole complexes of Fe-protoporphyrin IX and microperoxidase-8 and analyzed the pH dependence of these modes. The far-IR bands of the heme and the axial imidazole ligands were assigned using (15)N(2)-, and d(3)-imidazole isotopic substitution, as well as imidazole substitution by 4(5)-methylimidazole. Internal modes of the axial histidine and imidazole ligands were identified in the 670-580 cm(-1) region, which are sensitive to the iron coordination (five-coordinated high-spin heme or six-coordinated low-spin heme) and the protonation states of the axial ligands. We showed that deformation modes of the heme pyrroles dominate the 420-370 cm(-1) region of the difference spectra. These modes were highly sensitive to the coordination and redox states of the heme iron and the conformation of the tetrapyrrole. While no nu(as)(Fe-axial ligand) IR mode was detected in the difference spectra of the neutral imidazole complexes of Fe-protoporphyrin and microperoxidase, a new mode at 312 and 334 cm(-1) was found specific of the imidazolate complexes of Fe(3+)-protoporphyrin and Fe(3+)-microperoxidase-8, respectively. On the basis of isotope shifts observed upon ligand deuteration, this band was assigned to a mode mixing the asymmetric stretching of the axial bonds with an internal deformation of the imidazolate rings. These data set the bases for the analysis of the IR low-frequency modes of hemoproteins, and specifically the electronic properties of the heme axial histidine ligands.

Rb–Sr and U–Pb geochronology and setting of the Buffalo Head Hills kimberlite field, northern AlbertaThis article is one of a selection of papers published in this Special Issue on the themeGeology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers.

New Rb–Sr phlogopite and U–Pb perovskite age determinations for 12 of 38 known ultramafic bodies in the Buffalo Head Hills area of north-central Alberta show that kimberlitic magmatism occurred in at least two separate episodes during Late Cretaceous and Paleocene time. Nine kimberlites yield Coniacian to Campanian ages of between 88 ± 5 Ma (U–Pb perovskite, K5A) and 81.2 ± 2.3 Ma (Rb–Sr phlogopite, K252). A Danian U–Pb perovskite isochron age of 63.5 ± 0.7 Ma was obtained for the BM2 kimberlite, and Selandian Rb–Sr ages of 59.6 ± 2.8 and 60.3 ± 0.8 Ma were determined for the K1A and K19 bodies, respectively. These specific periods of magmatism correspond to characteristic intra-field features such as kimberlite spatial distribution, diamond content, rock classification, and mechanisms of emplacement. The ∼88–81 Ma group generally occurs in the northwestern part of the field and defines the diamond window for the Buffalo Head Hills kimberlite field. This volcanism is contemporaneous with sedimentary host rock deposition, which has important implications for the size and morphological complexity of the kimberlite bodies. The ∼64 Ma BM2 body represents the only known occurrence of hypabyssal-facies kimberlite in this field and is similar in terms of source composition to the ∼88–81 Ma kimberlites, but is not diamond bearing. The ∼60 Ma group occurs in the southwestern part of the field, is derived from a weakly diamondiferous – barren hybrid ultramafic source and features bodies that are eroded to present-day stratigraphic levels.

High hydrostatic pressure small-angle X-ray scattering cell for protein solution studies featuring diamond windows and disposable sample cells

A high-pressure cell for synchrotron small-angle X-ray scattering (SAXS) studies of protein solutions is described. The design was optimized for use at up to 400 MPa in liquid pressure and with 8−12 keV X-rays with particular emphasis on the ease of use. The high-pressure cell was fabricated from corrosion-resistant Inconel 725 (Special Metals Corporation, Huntington, WV, USA) and featured Poulter-type windows [Poulter (1932).Phys. Rev.40, 861–871]. Flat natural diamonds, 500 µm thick, were recycled from diamond anvil cells and were shown to perform well as high-pressure SAXS windows. For a simple and effective method of sample isolation, disposable plastic sample cells with a defined path length and reproducible parasitic scattering were designed. These sample cells enable efficient use of synchrotron time. The cells facilitate rapid and easy sample changes, eliminate the need to clean the cell between sample changes, and reduce the sample volume to as low as 12 µl. The disposable cells can also be used separately from the high-pressure cell for SAXS measurements at ambient pressure and temporary storage of samples. The performance of the apparatus is demonstrated with T4 lysozyme.